1. Field of the Invention
Aspects of the present invention relate to an optical disc apparatus, a method of performing an optical power study of an optical disc apparatus, and a method of detecting a writing power of an optical disc apparatus, and, more particularly, to an optical disc apparatus, a method of performing an optical power study of an optical disc apparatus, and a method of detecting a writing power of an optical disc apparatus, wherein an optical power study to determine characteristics of a light source according to an inputted optical power signal is performed on a specific area of an optical disc while maintaining a servo in a servo-on state so as to reduce a time required to perform the optical power study.
2. Description of the Related Art
An optical disc apparatus generally includes a laser diode to emit a laser beam toward an optical disc and a photodiode to receive the laser beam reflected from the optical disc so that the optical disc apparatus can write and read data onto and from the optical disc. To this end, the laser diode receives an optical power signal and emits a laser beam with a power corresponding to the optical power signal. Optical power signals corresponding respectively to optical powers are defined in a digital format. Each optical power signal is converted into an analog signal through a digital to analog converter (DAC), which is then applied to the laser diode. The laser diode then emits a laser beam with a power corresponding to the applied analog signal.
One characteristic of the laser diode is that the optical power of the emitted laser beam decreases as a temperature of the laser diode increases. Further, the characteristics of the DAC of each set slightly differ from those of other sets. Since the laser diode and DAC characteristics are, thus, not always uniform from one set to another, to achieve the optimal writing power, performing an optical power study to determine optical power characteristics of the laser diode of the set of interest is necessary. If a rewritable optical disc such as a CD-RW or a DVD-RW is inserted into the optical disc apparatus, the optical power study is performed during a lead-in process of the disc and, if a write-once optical disc such as a CD-R or a DVD-R is inserted, the optical power study is performed when the first write command is input.
There is no need to perform a process of writing or reading test data in the optical power study, which is generally a process of determining optical power characteristics of a laser diode. However, during the optical power study, data written on the optical disc may be damaged by a laser beam emitted as an optical power signal is applied to the laser diode. Accordingly, during the optical power study, the optical pickup including the laser diode is located as far as possible from the optical disc. FIG. 1 is a flow chart of a conventional method of performing an optical power study in the case where the optical power study is performed after a write command is input.
When a write button is pressed after an optical disc is inserted into the optical disc apparatus, a servo provided to perform focusing and tracking control is turned off in order to perform an optical power study (S110 and S120). During the optical power study, an actuator that is provided to drive a lens included in the optical pickup is moved down as low as possible in order to prevent damage to data that is written onto the optical disc. That is, the lens is located as far as possible from the optical disc (S130). The optical power study determines optical power characteristics of the laser diode by checking optical powers of laser beams emitted from the laser diode while sequentially applying a predetermined range of optical power signals to the laser diode (S140). Once the optical power study is completed, the actuator is moved up and the servo is turned on in order to perform Optical Power Calibration (OPC) to detect the optimal writing power (S150 and S160).
In the conventional optical power study method, a long time is required to turn the servo on/off and to move the actuator up and/or down in order to prevent damage to data written on the optical disc during the optical power study. This increases the total OPC time and a lead-in time during which unique information and the like of the inserted optical disc is read and stored.
Where the optical power study is performed after a write command is input, a high-capacity buffer is necessary to store data to be written that is input during the optical power study and the OPC, thereby increasing the manufacturing costs of the apparatus.